The physiological and biochemical responses of guayule to the low temperature of the Chihuahuan Desert in the biosynthesis of rubber

Studies on rubber formation in guayule in several field plantings support the conclusion that the low temperature of the fall and winter months of the Chihuahuan Desert promotes a rapid increase in rubber biosynthesis. There are definite changes in the cortical parenchyma during the biosynthesis and deposition of rubber. Discrete rubber particles are formed in the parietal and interior cytosol. Following the digestion of the cytosol in the interior of the cell and rubber particle fusion leaves the parenchyma with rubber deposits throughout the cells. The rubber transferase (RT) bound to the washed rubber particles (WRP-RT) catalyzes the formation of different length cis-1, 4-polyisoprene chains that collectively form the rubber polymer. The activities of the WRP-RT and the endoplasmic reticulum 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR) increase with exposure of the plant to low temperature and it is conceivable that these two enzymes play a pivotal role in the biosynthesis of rubber during this period. Thus guayule plants indigenous to the Chihuahuan Desert have developed a genetic system capable of responding to the low temperatures of the fall and winter of the desert culminating in the formation of rubber.